Airbag control unit with part number A1698204185

What does the airbag control unit A1698204185 do?

As the central control unit of the restraint system (SRS) of Mercedes-Benz, the airbag control unit A1698204185 processes the signals from all crash sensors. In the event of an accident, it decides within milliseconds which airbags and seatbelt pretensioners trigger. It monitors the system continuously and shows faults via the airbag warning light.

Seatbelt pretensioners and airbags are controlled by the same control unit, which is why its condition matters for the entire system.

After an accident, the unit stores crash data and locks itself.

Why does the control unit A1698204185 fail?

The most common cause is stored crash data after an accident, even if no airbag was triggered. A normal diagnostic tool cannot erase it. Other causes include aged components, cold solder joints, moisture on plugs and corrosion, and voltage spikes.

The record stays in the unit until Airbag24 removes it during the repair.

Aged components lose reliability over the years, while cold solder joints can give way under heat and vibration. Moisture and corrosion on the plugs interrupt connections, and voltage spikes, for example with a weak battery or a jump start, strain the electronics.

How can you tell that the A1698204185 is defective?

The airbag warning light in the instrument cluster stays on permanently or intermittently, and an error message is added. A diagnostic tool also finds no connection to the control unit, and the fault memory cannot be cleared.

When the warning light is on, airbags and seatbelt pretensioners may not trigger in an emergency. You should therefore have this warning checked promptly rather than ignore it.

It helps to note the driving conditions under which the light appeared. These details in particular make the later evaluation easier.

Which vehicles is the A1698204185 fitted in?

The control unit A1698204185 is fitted in these vehicles: Mercedes-Benz B-Class W245 (2005-2011); Mercedes-Benz A-Class W169 (2004-2012). Model and year of construction in your vehicle documents are decisive for the assignment.

The vehicles for comparison can be found here:

• Mercedes-Benz B-Class W245 (2005-2011)
• Mercedes-Benz A-Class W169 (2004-2012)

The part number on the label of the removed unit can be compared with this page. This ensures that it is the correct unit. It says nothing about the cause. Only a read-out fault memory shows whether the control unit itself is defective or whether a plug or a cable is behind it, so the read-out should take place before removal.

For the same vehicles, we also repair control units with the part numbers A1698201326, A1698202726, A1698204085, A1698206626, A1698206726, A1698207726.

How does the repair of the A1698204185 work?

You have the fault memory read out and attach the log, then disconnect the battery. Only then remove the control unit and create a repair order online. Then send the unit in well packed.

At Airbag24, the unit is examined on the test bench, defective components are repaired, stored crash data is erased, and then a function test follows. Inspection, repair and test usually take 3–4 working days there. Afterwards your own unit goes back to you.

Our repairs come with 2 years' statutory liability for defects. The repaired control unit comes back with all vehicle data and is ready for use as soon as it is refitted — no coding or programming is required.

How does the control unit A1698204185 get to Airbag24?

You send the unit as a parcel, or you book a UPS collection for an extra charge. Airbag24 returns it to you by UPS after the repair.

A printed repair order belongs in the parcel. Pack the unit shockproof before you hand it over.